In general, a conventional electron emission device includes a cathode that is capable of emitting electrons and an anode covered by phosphors that emit light when struck by the electrons. The anode and cathode are respectively aligned on substrates to allow the emitted light to form a picture.
According to a base structure of one type of such an electron emission device, a field emission display (FED), a cold cathode electron emission source is aligned on a cathode substrate with an anode on which is formed a phosphor layer pattern made up of a plurality of phosphor cells which are struck by an electron beam to provide a variety of colors.
A black layer that reduces reflection of external light and improves contrast of the device is formed between phosphor cells within the phosphor layer pattern. Methods to improve contrast include applying graphite within the phosphor layer pattern, adhering pigments on the surface of the phosphor layer pattern, or forming an insulating layer of non-conducting material within the phosphor layer pattern and then forming a conductive layer on it.
The first method of applying graphite between the phosphor layer has display quality and cycle life problems because impurities such as H2O, O2, CO, N2, CO2, etc. may be generated from the graphite. The second method of adhering pigments on the surface of the phosphor layer pattern has a problem of reduced luminance in devices driven at low voltages. The third method of forming an insulating layer of non-conducting material and forming a conductive layer on it, as disclosed in U.S. Pat. No. 5,534,749 and U.S. Pat. No. 6,002,205, may improve display quality and resolution. This improvement is due to the non-conductive insulating layer increasing contrast, and the conductive layer preventing display instability due to electron beam scattering which is caused by secondary electrons and charge buildup. However, this third method is very complicated because an insulating layer of non-conductive material is formed and etched, and then a conductive layer is formed thereon and then etched to obtain a pattern.